The state of the art can be defined by the following patents:
FR-A-1.460.927. The invention has for its object improvements in paint spray guns, and more particularly in their projection noses, and it concerns particularly the following points:
1) The combination of a liquid nozzle having an axial outlet and a multiplicity of radially diverging outlets about it, with a cap disposed to form annular air injection nozzles about each of these outlets; PA1 2) The addition, in front of the cap, of a member forming by its internal wall about the central outlet, an air injection nozzle and outlet of the corresponding mixture, and, by its external wall, a deflector pressing down against the spray jets supplied by the divergent outlets of the nozzle, said air jets passing through holes pierced through the cap about said member to stir the mixture supplied by the divergent outlets.
FR-A-2.194.135. Paint spray gun, characterized by the fact that the compressed air inlet in the channel of the handle is formed by a nozzle forming with its internal walls of said channel, a Venturi in which the secondary air drawn from outside ambient atmosphere, arrives by orifices provided in the Venturi about said nozzle.
EP 0 467 334. A sealing joint for an axle and an improved air valve for a portable paint spray gun, the joint having radial play with the securement axle except on the surface of the joint sealed along a limited axial length. The sealed joint of the axle has a radially conical surface external to the securement surface of the shaft so as to provide a sealing surface and for the transfer of axial forces from this surface in a radial direction permitting actuating the surface of the sealing joint relative to the axle. A second conical surface of the joint provides for the maintenance of the joint on the pneumatic spring of the air valve when the paint spray gun is dismounted. An improved air valve for portable paint spray guns is also described, having rigid axial means and a radial support supporting a portion of a relatively flexible rim and adapted to permit disengaging a conical sealed surface within the spray gun.
FR-A-2.548.555. Spray gun for paint, lacquer or analogous products, provided with a body in which are provided a nozzle for supply of the product to be pulverized, a needle for opening the closure of the orifice of said nozzle, a cap for drawing in air and a distribution ring for the air, or deflecting ring. According to the invention, this spray gun is characterized in that said air cap is fixed to said deflecting ring in a removable fashion.
FR-A-2.525.320. The invention relates to a joint adapted to ensure sealing of the fluids on the needle valves, spindles and other movable cylindrical objects. This joint comprises a packing which has a tubular end cut so as to have a sharp edge, and an abutment element which has a conical recess receiving the end, this latter and the recess surrounding the movable cylindrical object. A spring and a washer exert axial pressure on the packing inwardly of the cavity. Field of application: joints for paint spray guns, etc.
At present, sealing between the needle support or rod and the needle is ensured by pressure packing or by a sealing joint. This seal must prevent any passage of the product to be pulverized into the body of the spray gun.
According to the products to be pulverized, it is necessary to change the needle, however, there are always variations of diameter of the needles. In this case, it is absolutely necessary to again clamp the pressure packing; each manipulation of screwing or of unscrewing of the packing degrades the latter. Sealing problems rapidly arise, and the maintenance requires dismounting the spray gun assembly to recover the rest of the joint or pressure packing. These operations are therefore long and costly.